JPH0341923B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a transparent conductive film forming liquid suitable for a dipping method, and particularly to a transparent conductive film forming liquid containing an organometallic compound that becomes a transparent conductive metal oxide upon firing. It is well known that oxide films such as In, Sn, Sb, and Cd formed on insulating substrates such as glass and ceramics have high light transmittance and good conductivity, and are used in semiconductor devices and liquid crystal displays. It is used in equipment, etc., or as one of the components of electronic functional devices that involve light and electric fields, such as electrophotographic recording media, as well as photoelectric conversion elements such as solar cells and image pickup tubes, and transparent surface heat generating devices. It has been used as a functional film for bodies (decloster), transparent heat insulators, resistors, infrared reflectors, etc. Methods for forming this metal oxide transparent conductive film include chemical spray method, vacuum evaporation method, sputtering method,
There is a screen printing method. Although the chemical spray method is advantageous in obtaining a film with a relatively large area, it requires large-scale equipment and is difficult to control properties. Recently, the vacuum evaporation method has developed into a mask evaporation method, which eliminates the need for etching treatment, but since the treatment is performed in batches, there is a problem in terms of mass production. Like the vacuum evaporation method, the sputtering method is also a batch-type process, and therefore is not suitable for obtaining a large area. The screen printing method has disadvantages such as poor workability during printing, difficulty in stably printing particularly fine patterns, and large variations in the conductivity of the formed film. In recent years, the immersion method has attracted attention as a solution to these drawbacks. This method involves (a) applying an organometallic compound solution onto a substrate, (b) drying, (c) baking,
(iv) It is possible to form a film of any shape on a substrate through the simple process of etching, and it does not require large-scale equipment, and mass production is easy. Various materials have been studied as raw materials for this dipping method, but they have not been put to practical use due to various problems. That is, InCl ₃ , InNO ₃ ,
When using an organic solvent dispersion of an inorganic salt such as SnCl ₂ or SnCl ₄ , the formed film becomes cloudy.
There are disadvantages such as the membrane has low mechanical strength and is easily scratched. Furthermore, immersion liquids in which organic indium compounds such as indium octylate are dissolved have poor stability, and when applied to insulating substrates, hydrolysis occurs, causing the immersion liquid and coating to become cloudy, and transparent coatings to become cloudy. Even if obtained, physical properties such as area resistance and mechanical strength are insufficient. An object of the present invention is to provide a transparent conductive film-forming liquid that eliminates these drawbacks and provides a transparent conductive film with a long liquid life, low resistance, and high transparency and adhesion strength. The transparent conductive film forming liquid according to the present invention contains an organometallic compound that becomes a transparent conductive metal oxide upon firing, a resistance value adjusting agent, and an organic solvent that dissolves these. The organometallic compound has the general formula In×(X) _l (Y) _o
[X] is β-ketonic acid ester, Y is β-diketone, l = 1 or 2, m = 1 or 2, provided that l +
m=3]. The resistance value adjusting agent has the general formula (α) ₂ Sn
An organic tin compound represented by (β) ₂ [α is an alkyl group represented by the general formula CnH _2o+1 (where n=1 to 6) and β is β-diketones] is used. X in the general formula of the organic indium compound
Ethyl acetoacetate is preferred as a chelate-forming compound that is excellent in hydrolysis resistance, stability of immersion liquid, and economical efficiency. Among the organic tin compounds, dimethyltin acetylacetonate, diethyltin acetylacetonate, dibutyltin acetylacetonate,
Alternatively, tin dipropionate acetylacetonate is suitable because it increases the stability of the immersion liquid. The organic solvent used in the present invention is characterized by ease of volatilization in the drying process before firing, stability of the solution,
From the viewpoint of economy and the like, organic solvents with low boiling points, such as lower alcohols such as methanol and ethanol, esters such as ethyl acetoacetate, ketones such as methyl ethyl ketone, and benzene are suitable. Next, a method for forming a transparent conductive film on a substrate using the forming liquid of the present invention will be described. As the base material, a plate-shaped material such as glass or ceramic or another shape is selected depending on the purpose.
Further, the concentration of the forming liquid and the pulling speed are adjusted depending on the desired film thickness. After the forming liquid is applied onto the base material in this manner, it is dried. As for drying conditions, if the film is left at 140°C for 10 minutes, the solvent will evaporate sufficiently and a transparent film will be formed on the substrate. Next, it is baked in air at 500°C for 30 minutes. This treatment completely decomposes the organic matter and forms a transparent conductive film on the substrate. If the film thickness is insufficient after this one-time treatment, the same treatment is repeated to obtain a transparent conductive film having a desired thickness and excellent mechanical strength. The following will be described in more detail with reference to Examples. Example 1 Indium di-
Ethyl acetoacetate mono-acetylacetonate, [In

[Formula] (acac)] and indium mono-ethyl acetoacetate.
Diacetylacetonate [In

[Formula] (acac) ₂ ] We conducted repeated studies to find organic solvents in which these compounds are soluble. The results for indium di-ethylacetoacetate mono-acetylacetonate are shown in Table 1, and the results for indium mono-ethylacetoacetate di-acetylacetonate are shown in Table 2. Regarding the solution stability and solution transparency in the table, it is assumed that the condition immediately after adjustment is maintained without any precipitation, cloudiness, or foreign matter such as floating substances on the surface of the immersion liquid for one month after adjustment of the forming solution. Items that have been determined are marked with a ◎, items where there has been a change in the chemical properties described above are marked with an ○, and items where it has been determined that the immersion liquid has deteriorated significantly compared to immediately after adjustment are marked with an x. Regarding film formation properties during immersion, ◎ indicates excellent, 〇 indicates good, and ×
The mark is judged to be bad.

【table】

[Table] As is clear from these tables, methyl ethyl ketone, ethyl acetate, and benzene are preferred as organic solvents. The immersion liquid using these organic solvents was chemically stable for a long period of one month or more, and it was possible to obtain an immersion liquid without deterioration of the liquid.
Immersion liquids using alcohols such as methanol, ethanol, or ether as organic solvents are used after adjustment.
Precipitation occurs within 3 days, and crystalline suspended matter forms on the surface of the solution, resulting in a cloudy solution.
Transparency is significantly reduced. Next, we investigated organic tin compounds for adjusting electrical resistance. First, as an organic indium compound, indium
Di-ethylacetoacetate mono-acetylacetonate was used, and compounds shown in Tables 3 to 8 below were used as organic tin compounds for adjusting the resistance value. Six types of forming solutions were prepared using methyl ethyl ketone as an organic solvent. In these liquids, the amount x of the above organotin compound added
5.0, 10.0, 12.0, 15.0, for all organometallic
It was regulated at 20.0% by weight. (Organic metal) Γ〔In

[Formula] (acac)] 10 x (1-x/100) weight% Γ [organotin compound] 10 x (x/100) weight% (solvent) Γ methyl ethyl ketone 90 weight% However, x accounts for the total organic metal This is the proportion of organotin compounds. A soda glass substrate measuring 50 mm x 25 mm x 1 mm was immersed in the above forming solution. The substrate was pulled up from the solution at a pulling speed of 20 cm/min and pre-dried at 140°C for 10 minutes. Next, it was baked in a belt furnace at 500°C for 30 minutes to obtain a transparent conductive film on the glass substrate. The results of measuring the surface resistance, film thickness, light transmittance, and film strength of this film are shown in Tables 3 to 8 below.

【table】

【table】

【table】

【table】

【table】

[Table] As is clear from these tables, in any case, the amount x of the organic tin compound added is preferably in the range of 10 to 15% by weight based on the total amount of organic metal. Among organic tin compounds, the forming solution using dibutyltin acetylacetonate (C ₄ H ₉ ) ₂ Sn(acac) ₂ is
It has the lowest sheet resistance value among the six types of solutions. Example 2 Among the organic indium compounds whose solubility was investigated in Example 1, indium mono-ethyl acetoacetate di-acetylacetonate was used, and six types of organic tin compounds similar to those in Example 1 were used as organic tin compounds for adjusting electrical resistance. A forming solution was prepared using an organic tin compound, and the film properties similar to those in Example 1 were investigated. As a result, as described in Example 1, those in which the amount x of the organic tin compound added was 10 to 15% by weight had a low areal resistance value, and the one using dibutyltin acetylacetonate had the lowest areal resistance value. It had Example 3 In order to determine an appropriate total organometallic content, a forming liquid having the following composition was prepared. (Metal part) Γ indium di-ethylacetoacetate mono-acetyl acetonate
...0.875ywt% Γdibutyltin acetylacetonate
...0.125y% by weight (solvent part) Γ methyl ethyl ketone 100-y parts by weight, where y is the total organic metal content. A film was formed on a soda glass substrate using the prepared forming solution under the same conditions as in Example 2, and the physical properties of the film were investigated and summarized in Table 9 below. Regarding solution stability in the table, those that can be used without chemical change for more than 20 days are marked with ◎, and 10
Items that can be used for more than 20 days are marked with ○, and items that can be used for less than 10 days are marked with △. Regarding film formation properties during immersion, those that become cloudy after immersion and have noticeable unevenness in film thickness are marked with an ×, those that do not become cloudy and have almost no unevenness in film thickness are marked with ○, and those judged to be particularly excellent are marked as ◎ Marked.

【table】

[Table] As is clear from this table, those having a total organometallic content y of 15 to 30% by weight, preferably 25 to 30% by weight, have various excellent properties. Example 4 The same study as in Example 3 was conducted using indium mono-ethylacetoacetate di-acetylacetonate as the organic indium compound, and almost the same results as in Table 9 were obtained. The figure shows the storage characteristics of each forming solution. Curve A in the figure is for a forming solution using indium di-ethylacetoacetate mono-acetylacetonate and dibutyltin acetylacetonate, and curve B is for the forming solution using indium di-ethylacetoacetate mono-acetylacetonate. Ethylacetoacetate・
Curve C is for a forming solution using diacetylacetonate and dibutyltin acetylacetonate, and curve C is for a comparative forming solution using indium octylate and dibutyltin acetylacetonate. In addition, in this comparative example, the liquid became cloudy after being stored for 10 days and could not be used thereafter. As is clear from this figure, the film obtained in the comparative example has a high sheet resistance value, and furthermore, the characteristic value changes depending on the number of days of storage. On the other hand, in the case of forming liquids A and B according to the present invention, the film obtained has a low sheet resistance value, and even when stored for a long period of time, there is almost no change in characteristic values and the performance is stable. As described above, the present invention uses an organic indium compound such as indium di-ethylacetoacetate mono-acetylacetonate or indium mono-ethylacetoacetate di-acetylacetonate as an organic metal compound to stabilize the solution. A solution with excellent properties, solution transparency, and film-forming properties during immersion can be obtained. In addition, as electrical resistance value adjusting agents, dimethyltin acetylacetonate, diethyltin acetylacetonate, dibutyltin acetylacetonate,
Using an organotin compound selected from the group of tin dipropionate acetylacetonate, and adding the organotin compound in an amount of 10% relative to the total organometallic amount of the organoindium compound and the organotin compound.
By regulating the content within the range of ~15% by weight, it is possible to form a coating having a low sheet resistance value and high adhesion strength to the substrate. Furthermore, by regulating the total amount of organometallic (organoindium compound + organotin compound) in the total amount of the forming solution to a range of 15 to 30% by weight, we have achieved performance that shows almost no change in characteristic values even after long-term storage. It is possible to provide a transparent conductive film forming liquid that is stable in terms of performance.

[Brief explanation of drawings]

The figure is a characteristic curve showing how the characteristic values change as each forming solution is stored.

Claims (1)

[Scope of Claims] 1 Contains an organometallic compound that becomes a transparent conductive metal oxide upon firing, an electrical resistance regulator, and an organic solvent that dissolves the organometallic compound and the electrical resistance regulator. In the transparent conductive film forming liquid, the organometallic compound is an organic indium compound of indium di-ethylacetoacetate mono-acetylacetonate or indium mono-ethylacetoacetate di-acetylacetonate, and the electrical resistance value is the modifier is an organotin compound selected from the group of dimethyltin acetylacetonate, diethylstin acetylacetonate, dibutyltin acetylacetonate, and tin dipropionate acetylacetonate; The amount of the organotin compound added to the amount of organic metal is regulated in the range of 10 to 15% by weight, and the total amount of organic metals of the organic indium compound and the organotin compound is contained in the total amount of the forming liquid at 15 to 30% by weight. A transparent conductive film forming liquid characterized by: